The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The accurate setting of the suspension system of a vehicle at the design position for the vehicle height improves passenger comfort, vehicle handling performance and the visual aspects of the vehicle. The design position for the vehicle height is directly related to the design length of the McPherson suspension module or the pseudo McPherson suspension module mounted on the vehicle. Typical vehicle height tolerances can vary from about ±7 mm to about ±10 mm. If the vehicle manufacturer wants to reduce these tolerances, significant extra efforts are required and special manufacturing techniques need to be developed resulting in significant additional costs.
Vehicle manufacturers establish what the design height or vehicle height of the vehicle and thus the McPherson suspension module should be. Typically, a vehicle manufacturer will determine a specific weight of the vehicle at which the design height is defined. The specific weight can include the driver, a passenger and a specified weight for baggage of the driver and the passenger. At this specific weight of the vehicle, the nominal vehicle height and the allowed tolerances are defined.
A typical McPherson suspension module comprises a top mount connecting the module to the car body, a bearing for allowing rotation of the wheel, a spring supporting the vehicle's weight, a strut or damper providing vehicle damping, an upper and a lower spring seat supporting the spring and an anti-roll bracket to connect the anti-roll link to the strut or damper.
The achieved McPherson suspension module tolerance will be a combination of the tolerances of the top mount, the bearing, the spring, the upper seat position, the lower seat position on the strut and the positioning tolerances (in height) of the strut or damper into the knuckle. Typical design methods that ensure a correct positioning of the strut or damper into the knuckle include a reduced diameter for the strut or bearing that is inserted into the knuckle, a local area of the strut or damper tube is increased to act as a stop for the knuckle, a hook-shaped bracket can be welded to the strut or damper tube which acts as a stop for the bolt extending through the knuckle, or a T-shaped bracket can be welded to the strut or damper tube which acts as a stop in both a vertical and an angular position. The utilization of one of these methods also adds the tolerances of these components to the cumulative tolerances of the vehicle height.
In order to minimize the height tolerances of the assembled McPherson suspension module, you can individually reduce the tolerances for each of the components discussed above. This typically only results in a minimal reduction of the overall tolerance band and can lead to significantly higher manufacturing costs.